The lubrication oil of internal combustion engines is heated as it works, and if its temperature becomes too high, it risks degrading, which poses problems for its filtration by the filtering element, generally consisting of paper.
In order to overcome this drawback, it has already been proposed to cool the oil Just before its filtration by making the side wall of the casing of the oil filter consist of a heat exchanger defining two entwined circuits one of which is intended for the oil before its filtration and the other for a cooling liquid.
The invention relates more particularly, amongst the oil filters of the type in question, to those for which the heat exchanger consists of two coaxial cylindrical sleeves which surround one another, and of an intermediate partition of generally cylindrical shape, but deformed, and arranged in the annular space lying between the two sleeves.
In the known embodiments of these oil filters, the deformed intermediate partition consists of a cylindrical sheet which is folded axially so as to form a succession of grooves and ribs which are annular and of revolution and whose axial half-section exhibits a substantially sinusoidal shape (see document WO-A-88/06228).
These constructions exhibit advantages, but also certain drawbacks, including the following:
the portion of the oil circuit included by the exchanger, along which portion the heat is transmitted from each of the small volumes of oil to the cooling liquid, extends over a quarter of a circle only, PA1 the cross-section of the intermediate sheet portion which defines each of the two heat exchange circuits exhibits the shape of a U with smooth walls, which shape is imposed by the folding. PA1 the circuit reserved for the cooling liquid comprises several helical segments connected in parallel, PA1 in a filter according to the preceding point, each helical segment extends over 1.5 turns, PA1 the cross-section of at least one of the grooves exhibits the general profile of a U with lateral cutouts projecting towards the inside of the U.
The invention allows these drawbacks to be overcome.